PHARR, TEXAS — A TEXAS water official focuses his binoculars on the ''secret'' pumps on the opposite banks of the Rio Grande, watching powerlessly as they suck a steady torrent into a Mexican irrigation canal.
Ruben Quintanilla says Mexican farmers are taking water that belongs to Texas in broad daylight.
''They are just sticking in 100 of them right and left,'' Mr. Quintanilla, a deputy for the Rio Grande water master, says of the pumps. ''They don't care. They are desperate right now.''
Illegal pumping from the Rio Grande is only one sign of a serious international water shortage. Reservoirs that augment the muddy border river are perilously low; experts say the key source of water in this semiarid delta could run dry.
Mexican border cities might soon be asking for loans from Texas reserves -- a prospect that causes many Texans to bristle, including Gov. George W. Bush.
''Texas will not support a loan of Texas water to Mexico, as this would jeopardize the welfare of many of our citizens,'' Bush wrote recently in an open letter to John Bernal, the United States commissioner on the two-nation International Boundary and Water Commission.
In the letter, Mr. Bush estimated the potential economic impact on Texas of the water losses at $500 million to $1.5 billion.
Mexico has continued heavy irrigation despite a drought that began almost two years ago in Chihuahua, the northern state whose watershed supplies most of the water in two major Rio Grande reserves, Amistad Reservoir and Falcon Lake, says John Hinojosa, the Rio Grande water master for Texas.
Mexico has used all but 6.4 percent of its allotments from the water stored behind those two crucial dams. Texas, which shares the reservoirs with Mexico, is expected to drain down to half its allotments by July.
Experts say that unless major rains hit upstream between Chihuahua and West Texas, Mexico could exhaust its reserves by June. Mr. Hinojosa projects that most Texas farmers will have enough water to bring crops to harvest this summer, but they could wind up with nothing for irrigation next year. They could run out even sooner if Mexico doesn't ease off.
While Bush and other Texas officials talk tough about granting extra water to Mexico, Bob Peterson, president of Starr Produce Company in Rio Grande City, sees such water loans as an inevitability of tough times along a shared river.
''Do we irrigate our field, or watch our Mexican neighbor die for lack of water?'' he says.